1. Field of the Invention
The present invention relates to an image formation apparatus, a color conversion program embodied on a computer readable medium, and a color conversion method, and more particularly to an image formation apparatus converting data generated to be printed on a first printer into data to be printed on a second printer, a color conversion program embodied on a computer readable medium to be executed in the image formation apparatus, and a color conversion method.
2. Description of the Related Art
The color management system is known as a technique for adapting to differences in color reproducibility among different devices. The ICC (International Color Consortium) profile, which describes color-related characteristics for each device, is used in the color management system. A color conversion lookup table is generated using the ICC profile of an input device and the ICC profile of an output device thereby to facilitate conversion from color data for output on the input device into color data for output on the output device.
In the color conversion lookup table, in order to relate a predetermined plurality of lattice points in a device space (color system) of an input device with a predetermined plurality of lattice points in a device space of an output device, output data converted for the output device using the color conversion lookup table should be interpolated in a case where first color data generated for the input device is located between a plurality of lattice points. Japanese Examined Patent Publication No. 58-16180 discloses a method of color conversion using four lattice points that constitute the vertexes of a triangular pyramid enclosing a pixel of color data to be subjected to color conversion, among a plurality of lattice points in a device space of an input device as defined by a three-dimensional lookup table. The conventional color conversion method can be applied not only to a case where color data is three-dimensional but also to a case where it is N-dimensional (where N is an integer equal to or larger than four).
On the other hand, the color space for use in image data is generally a three-dimensional device space in RGB color system. Therefore, an output device is installed with existing hardware or program for operating the above-noted interpolation when color data is converted from the three-dimensional device space into the device space of the output device. The existing hardware or program is hardware or a program for executing an interpolation process for relatively low dimensions, for example, as in the expression (8) shown later.
However, when the device space of color data is not three-dimensional, the conventional color conversion method has to be used, and the existing hardware or program that the device originally has cannot be used.
Furthermore, Japanese Patent Laid-Open No. 10-307911 discloses a technique for determining a lattice point to be interpolated in three-dimensional interpolation and a weight coefficient in the interpolation operation by sorting lower-order bits of input data in descending order. However, when the technique disclosed in Japanese Patent Laid-Open No. 10-307911 is applied to input data having dimensions larger than three dimensions, the number of times operations are performed is increased due to the sorting processing, thereby increasing the processing time.